KR19980048083A - Method of manufacturing magnetic recording medium - Google Patents

Abstract

The present invention forms a first nonmagnetic layer adjacent to a nonmagnetic support by using a coating solution prepared by dispersing ferromagnetic powder and carbon black in a binder solution on a nonmagnetic support, and forms ferromagnetic powder and carbon black on the binder solution. The total volume ratio of the carbon black and the ferromagnetic powder contained in the first non-magnetic layer in the preparation of the magnetic recording medium by forming the coating liquid dispersed in the second magnetic layer and then aligning, drying, surface smoothing, curing and cutting. Is 1.0 to 7.5, the total specific surface area ratio of carbon black and ferromagnetic powder is 2 to 16, the total volume ratio of carbon black and ferromagnetic powder in the second magnetic layer is 0.02 to 0.3, and the total specific surface area ratio of carbon black and ferromagnetic powder is 0.05. It relates to the manufacture of a magnetic recording medium of ˜0.6.

Description

Method of manufacturing magnetic recording medium

1 is a cross-sectional view of a magnetic recording medium of a laminated structure according to the present invention.

2 is a cross-sectional view of a conventional magnetic recording medium in which only a magnetic layer is laminated on a nonmagnetic support.

* Description of the symbols for the main parts of the drawings *

I: Nonmagnetic Support II: Nonmagnetic Layer

Ⅲ: magnetic layer

The present invention relates to a method of manufacturing a magnetic recording medium for forming a magnetic layer on a nonmagnetic support.

Conventionally, a method of manufacturing a magnetic recording medium made of a magnetic tape such as an audio tape or a video tape and a magnetic disk such as a floppy disk is applied to form a magnetic layer by applying a magnetic coating solution on a nonmagnetic support having a larger area than a conventional product. After drying by performing an orientation treatment or the like, the magnetic layer is subjected to surface smoothing to make a disc of a magnetic recording medium. Thereafter, the final product is completed through a curing process. As a final process, the cassette, which is the final product of the next step, may be produced by a process such as casing.

The magnetic coating solution is prepared by dispersing other inorganic materials such as ferromagnetic powder, alumina carbon black, lubricants, hardeners, and dispersants in a binder solution, and the surface smoothing treatment improves the smoothing and filling density of the surface of the magnetic layer. , Uniformity of coating thickness and the like can be achieved. Smoothing of the surface of the magnetic material is very effective for improving the reproduction output of the magnetic recording medium and reducing the noise.

Due to the recent development of magnetic recording systems and high-density recording technologies, it is necessary to manufacture a recording medium having a large storage capacity of the magnetic recording medium. Therefore, it is necessary to increase information memory per unit area of the recording medium.

Therefore, in order to increase the density of the information recording, it is necessary to concentrate the recording magnetic flux generated from the magnetic head for recording and reproducing the information in a small area, so that the magnetic head becomes smaller and the amount of magnetic flux generated is reduced. Therefore, in order to locally reverse the magnetization direction of the magnetic body in the magnetic flux to be reduced as described above, complete magnetization reversal is possible by reducing the magnetic layer volume, that is, reducing the thickness of the magnetic body. However, when the volume of the magnetic layer is reduced, the light shielding effect may be reduced, the surface property may be reduced due to the formation of a thin film, the characteristics may be reduced due to the surface property, the dropout may be increased, and the durability may be reduced.

As shown in FIG. 2, a conventional magnetic recording medium is prepared by forming a magnetic layer (III) coated with a magnetic coating solution prepared by dispersing ferromagnetic powder in a solution on a nonmagnetic support (I), wherein the magnetic recording medium The thickness of is applied over 17㎛ in VHS standard. Therefore, the conventional tape uses a high-molecular material such as polyethylene terephthalate having a thickness of 13 to 16 μm in a nonmagnetic support, and manufactures a magnetic recording medium by applying or depositing a magnetic layer having a thickness of about 2 to 4 μm thereon. Alternatively, two or more kinds of magnetic materials are dispersed in a binder solution, and in this case, since the coating layer is one layer, there is a limit to satisfy all the characteristics required for the magnetic recording medium.

Therefore, the present inventors have studied to solve the above problems and found that the application form and the volume concentration of the magnetic layer formed on the nonmagnetic support play an important role in determining the characteristics of the medium. Separation of roles led to the following invention.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a high quality magnetic recording medium capable of high density recording, excellent magnetic properties, and particularly excellent electron conversion characteristics.

Specifically, the present invention forms a first nonmagnetic layer adjacent to the nonmagnetic support by using a coating solution prepared by dispersing ferromagnetic powder and carbon black in a binder solution on a nonmagnetic support, and the ferromagnetic powder is placed on the binder solution. The total volume ratio of carbon black and ferromagnetic powder contained in the first non-magnetic layer was 1.0 when the magnetic recording medium was formed by drying, surface smoothing, curing, and cutting after forming the coating liquid dispersed in the second magnetic layer. ~ 7.5, the total specific surface area ratio of carbon black and ferromagnetic powder is 2-16, the total volume of carbon black and ferromagnetic powder contained in the second magnetic layer is 0.02-0.3, and the total specific surface area ratio of carbon black and ferromagnetic powder is 0.05-0.6 The present invention relates to the production of a magnetic recording medium.

Hereinafter, the present invention will be described in more detail.

1 is a cross-sectional view of a magnetic recording medium prepared according to the present invention, in which a nonmagnetic layer (II) as a first layer is formed by dispersing in a binder solution containing ferromagnetic powder and carbon black as main components on a nonmagnetic support (I). The magnetic layer (III) to which the magnetic coating liquid prepared by disperse | distributing the ferromagnetic powder which is a 2nd layer to a binder solution was formed on it.

Hereinafter, the present invention will be described in more detail. The present invention is a non-magnetic prepared by dispersing a substance such as a lubricant and a dispersant in a binder solution, using ferromagnetic powder and carbon black as main components on a nonmagnetic support composed of a polymer material such as polyethylene terephthalate. After preparing the coating liquid through a high dispersion process, the first non-magnetic layer is formed, and inorganic materials such as ferromagnetic powder, abrasive, and carbon black, and lubricants, curing agents, and dispersants are dispersed in the binder solution through a high dispersion process. After applying a magnetic coating liquid to form a second magnetic layer, and after the orientation, dry surface smoothing, hardening and cutting process, the method for manufacturing a magnetic recording medium having excellent runability and running durability, and particularly excellent electron conversion characteristics. It is about.

As the nonmagnetic support of the present invention, known films such as polyethylene terephthalate, polyethylene naphthalate, polyaramid, polycarbonate, polyamide, polyimide, polyamideimide and aramid can be used.

The non-magnetic support has a centerline average surface roughness of 0.1 m or less, preferably 0.05 m or less. In addition, such nonmagnetic supports not only have to have a low center line average surface roughness but also have no coarseness of 1.0 µm or more. In addition, the shape of the surface roughness can be freely controlled by a pillar to be added as needed, and such a pillar may be an oxide such as Ca, Si, Ti, and organic fine powder such as carbonate and acrylic.

The ferromagnetic powder that can be used in the magnetic layer is not particularly limited. Examples include γ-Fe ₂ O ₃ , Co containing, γ-Fe ₂ O ₃ , Fe ₃ O ₄ , Co containing Fe ₃ O ₄ , CrO ₂ , Co-Ni-P alloy, Fe-Co-Ni alloy, barium ferrite Known ferromagnetic powders, such as strontium ferrite, may be used, and Co-containing γ-Fe ₂ O ₃ , Co-containing Fe ₃ O ₄ , and the like may be used.

As the abrasive, inorganic materials such as alpha ferrite, SiO ₂ , TiO ₂ , ZrO ₂ , SnO ₂ , Sb ₂ O ₃ , Cr ₂ O _3, and Al ₂ O ₃ may be used.

Types of carbon black that can be used include special blacks or rubber blacks. Specifically, the type of pellets (beads) or powder type carbon blacks having a particle size of 40 nm or less is black pulsel on the robot, Regal 600 series Vulcan 9A32, Vulcan P, Monarch 880, Monarch 800, Black Pearl 880, Black Pearl 800, Vulcan XC-72, Regal 330R, Regal 99R, and Degussa's Princedex series, Princedex 85, 75, L, 55, 45 , 40, 35, Colombian Raven 2000, Conducttex 900, Raven 1250, 1170, 1020, 850 and Mitsubishi's # 850, MCF 88, MA600, # 3150, # 45, # 47, # 44, # 33, CF9, etc. Lucky's high black series 600L, 60L, 50LB, 40B1, 40B2, 45LB, 40L, 30L, 30LB, 20L, 5L, 40, 30, 20B, 20, 20B, 10, 10B, etc. And Peltel (bead) or powder type carbon black having a particle size of 40 nm or more. 130, Monarch 120 and the like. Degussa's Princedex A, G Colombian's Raven 14, 430 Mitsubishi's # 20, # 10 Lucky's High Black 150B, 160B and the like can be used alone or in combination.

Examples of the lubricant include ester fatty acids and fatty acids, and specifically, lauric acid, myristic acid, stearic acid, butyl stearate, oleic acid, oleyl alcohol, lauryl alcohol and the like can be used alone or in combination.

Available dispersants include, for titanium, isopropyl triisostearolyl titanate, isopropyl tri (dodecyl) benzenesulfonyl titanate, isopropyl tri (dioctyl) phosphato titanate, isopropyl tri (di Octyl) pyrophosphate titanate, isopropyl triethyl titanate and the like can be used, and as the aluminum type, diisobutyl (oleyl) aceto acetyl aluminate, diisopropyl (oleyl) acetoacetyl aluminate, acetoalkoxy Aluminum diisopropylate and the like can be used.

As the binder, a vinyl chloride-based resin, a urethane-based resin, and a mixed system separated from a polyisocyanate-based compound may be used, and for each binder, -COOM, -OSO ₃ M, -SO ₂ M, PO (OM ₁ ) (OM ₂ ) ), -OPO (OM ₁ ) (OM ₂ ), NR ₄ X (where M, M ₁ , M ₂ represents Li, Na, K, H, -NR ₄ or HNR ₃ , and R represents an alkyl group or H And X represents a halogen atom.), Specifically, Union Carbide's UCAR-527, UCAR-569, VAGH, VYHH, VMCH, VAGF, VAGD, VROH, VYES. , VYNC, VMCC, XYHL, XYSG, PKHH, PKHJ, PKHC, PKFE, etc. MPR-TA, MPR-TA5, MPR-TAL, MPR-TSN, MPR-TMF, MPR-TS, MPR-TM, MPR 100OW, DX80, DX82, DX83, 100FD from TAO, etc., and MR105, MR100, MR-110 from Japan, etc., Nipponan N2301, N2302, N2304 from Japan Polyurethane, Pantex T-5105, from Japan Nippon Inks, etc. T-R3080, T-5201, etc., CA-271, CA-237, CA-2 from Molton 237, CA-236, CA-239, CA-397, CA-398, CA-399, 84847, CA-151HT, CA-152, etc., TI-9200, TI-1331, TI-8222, TI-8202, TI-8321, TI-8405, TI-8550, TI-8800, TI-8860, TI-8870, TI-8890, TI-8900, TI-8911, TI-8912 and 5714F1 from BF Goodrich, 5703P, 5701F1P, 5788P, 5719P, 5715P, 5706P, 5755P, 5778P, 5799P and the like can be used.

As a hardening | curing agent, the isocyanate type hardening | curing agent etc. containing a suitable amount of NCO group can be used. Specifically, triylene diisocyanate, 4-4 'diphenylmethane diisocyanate, hexamethylene diisocyanate, xylene diisocyanate, naphthylene-1, 5- diisocyanate, triphenylmethane triisocyanate, etc. can be used.

The organic solvent which can be used as a solvent is ketones, such as acetone, methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, and cyclohexanone, methanol, ethanol, propanol, butanol, isobutyl alcohol, and isopropyl alcohol in arbitrary ratios. Alcohols such as methylcyclohexanone, esters such as methyl acetate, butyl acetate and isobutyl acetate, glycol ethers such as glycol dimethyl ether, glycol monoethyl ether and dioxane, aromatics such as benzene, toluene and chlorobenzene Chlorinated hydrocarbons such as hydrocarbons, methylene chloride, ethylene chloride and carbon tetrachloride may be used. Such organic solvents are not necessarily 100% pure and preferably 10 to 30% or less of isomers, side reactions, and decomposed products in addition to the main components. There may be less than 10% of impurities below.

Initially disperse the inorganic materials such as the usable magnetic material, carbon black and abrasive in the binder solution in an appropriate amount suitable for the purpose, and then add the auxiliary materials such as the binder, lubricant, and hardener, and then prepare or paint again through the dispersion process. Using the technique of to prepare a paint for the above purpose.

The coating is applied in a predetermined volume in a simultaneous or a series of orders on a non-magnetic support that runs at high speed, followed by drying, smoothing, curing, and cutting to prepare a magnetic recording medium. Since the carbon black contained in the coating liquid of the present invention occupies a relatively higher content than the carbon black contained in the second magnetic layer, the rheological behavior such as thixotropic and Newtonian characteristics of the magnetic coating is simultaneously maintained. Will appear. In other words, it exhibits Newtonian behavior at low shear, such as pipe flow of paint, and thixotropic properties at high shear, such as when applied, and thus has good applicability and leveling after application. ) Can also show good results. In addition, since the content of the carbon black contained in the first nonmagnetic layer is higher than the content of the carbon black contained in the second magnetic layer, the light shielding effect is excellent and the surface property is good, so that the surface property is good when forming the second magnetic layer. As the second magnetic layer is designed to be lower than the content of carbon black used in forming a single layer, it is possible to improve the electron conversion characteristics and improve the dropout yield and to form the second magnetic layer at a thickness necessary for magnetic recording. Savings are possible. In addition, the surface instability of the entire magnetic coating film is excellent because the problem of interface instability during simultaneous middle layer coating can be solved by the rheological behavior. The first nonmagnetic layer and the second magnetic layer will be described in more detail. The second magnetic layer should be coated with a thin film in order to enable local magnetization reversal. It is disadvantageous to secure the properties, and the content of secondary raw materials other than the ferromagnetic material that is involved in the magnetic recording in the magnetic layer is high overall, which limits the performance of the ferromagnetic material. Therefore, the second magnetic layer is designed around the ferromagnetic powder involved in the magnetic recording to provide a high quality magnetic recording medium with excellent electron conversion characteristics and excellent dropout, and the first non-magnetic layer is relatively high relative to the content of the ferromagnetic powder. By increasing the content of carbon black, it is possible to design around the light shielding effect as well as the necessary charging effect and durability of the magnetic recording medium. In addition, since the content of carbon black with very small particles is high when forming the first nonmagnetic layer, it is possible to impart excellent surface properties compared to the surface property of the nonmagnetic support. Therefore, it is possible to prepare a magnetic recording medium having excellent surface properties when forming the second magnetic layer. Since the first non-magnetic layer contains ferromagnetic powder, the thixotropic property of the magnetic chart appears, so that the coating can be secured with low viscosity behavior when applied, and the coating property is excellent. By controlling the rheological behavior of the two layers, it is possible to manufacture a magnetic recording medium having excellent stable surface properties of the two layers by eliminating stress unevenness and unstable phenomena of the interface. In addition, the first non-magnetic layer does not require the addition of an abrasive and has a low content of bulky carbon black, which plays an advantageous role in the cost of the magnetic recording medium. By selecting a type of lubricant, a lubricant is added to each layer to show an appropriate effect. It is possible to manufacture a high quality magnetic recording medium having excellent running and running durability.

Therefore, according to the present invention, it is possible to provide a high-quality magnetic recording medium having excellent running characteristics, driving durability, light shielding effect, surface properties, electron conversion characteristics, etc., as well as economical savings.

Hereinafter, the present invention will be described in detail with reference to Examples, but the scope of the present invention is not limited by Examples.

[Examples and Comparative Examples]

Composition of the first nonmagnetic layer

Ferromagnetic powder: 5 to 60 parts by weight

Magnetite, Co-γ-Fe ₂ O ₃ or γ-Fe ₂ O ₃

Carbon black: 15 to 35 parts by weight

PU binder: 30 parts by weight

Lubricant: 3 parts by weight

[Myric acid]

Dispersant: 2 parts by weight

[Isopropyltri (dodecyl) benzenesulfonyl titanate]

Curing agent: 5 parts by weight

[Trillel Diisocyanate]

Organic solvent: 100 parts by weight of cyclohexanone

100 parts by weight of methyl ethyl ketone

Toluene 90 parts by weight

-The content of ferromagnetic powder and carbon black is changed according to Examples and Comparative Examples.

Composition of the second magnetic layer

Ferromagnetic powder: 100 parts by weight

Carbon black: 0.5-20 weight part

PU binder: 25 parts by weight

Lubricant: 0.1 to 5 parts by weight

Dispersant: 0.05 to 4 parts by weight

Curing agent: 3 to 9 parts by weight

Organic solvent: 150 parts by weight of cyclohexanone

150 parts by weight of methyl ethyl ketone

130 parts by weight of toluene

-Change the content of carbon black based on the powder

With the above composition, the first nonmagnetic layer and the second magnetic layer were applied onto the nonmagnetic support in a simultaneous or a series of steps to produce a magnetic recording medium.

Example 1

On the nonmagnetic support, a first nonmagnetic layer is formed such that the total volume ratio of carbon black and ferromagnetic powder in the composition is 1.0 and the total specific surface area ratio is 2.2, and the total volume ratio of carbon black and ferromagnetic powder in the composition The second magnetic layer was formed so that the ratio was 0.26 and the total specific surface area ratio was 0.55, thereby producing a magnetic recording medium.

Example 2

On the nonmagnetic support, a first nonmagnetic layer is formed such that the total volume ratio of carbon black and ferromagnetic powder in the composition is 1.4 and the total specific surface area ratio is 3.0, and the total volume ratio of carbon black and ferromagnetic powder in the composition The second magnetic layer was formed to have a value of 0.16 and a total specific surface area ratio of 0.33 to produce a magnetic recording medium.

Example 3

On the nonmagnetic support, a first nonmagnetic layer is formed such that the total volume ratio of carbon black and ferromagnetic powder in the composition is 2.1 and the total specific surface area ratio is 4.4, and the total volume ratio of carbon black and ferromagnetic powder in the composition The second magnetic layer was formed to have a value of 0.1 and a total specific surface area ratio of 0.22, thereby producing a magnetic recording medium.

Example 4

On the nonmagnetic support, a first nonmagnetic layer is formed such that the total volume ratio of carbon black and ferromagnetic powder in the composition is 7.3 and the total specific surface area ratio is 15.5, and the total volume ratio of carbon black and ferromagnetic powder in the composition Was formed so that the second magnetic layer was 0.06 and the total specific surface area ratio was 0.11, thereby producing a magnetic recording medium.

Comparative Example 1

On the nonmagnetic support, a first nonmagnetic layer is formed such that the total volume ratio of carbon black and ferromagnetic powder in the composition is 15 and the total specific surface area ratio is 32, and the total volume ratio of carbon black and ferromagnetic powder in the composition The second magnetic layer was formed so that 0.0 and total specific surface area ratio became 0.0, thereby producing a magnetic recording medium.

Comparative Example 2

On the nonmagnetic support, a first nonmagnetic layer is formed such that the total volume ratio of carbon black and ferromagnetic powder in the composition is 2.1 and the total specific surface area ratio is 4.4, and the total volume ratio of carbon black and ferromagnetic powder in the composition The second magnetic layer was formed so that 0.36 and the total specific surface area ratio was 0.78, thereby producing a magnetic recording medium.

Comparative Example 3

On the nonmagnetic support, a first nonmagnetic layer is formed such that the total volume ratio of carbon black and ferromagnetic powder in the composition is 15 and the total specific surface area ratio is 32, and the total volume ratio of carbon black and ferromagnetic powder in the composition The second magnetic layer was formed to have a value of 0.1 and a total specific surface area ratio of 0.22, thereby producing a magnetic recording medium.

[Comparative Example 4]

On the nonmagnetic support, a first nonmagnetic layer is formed such that the total volume ratio of carbon black and ferromagnetic powder in the composition is 0.5 and the total specific surface area ratio is 1.0, and the total volume ratio of carbon black and ferromagnetic powder in the composition The second magnetic layer was formed so that 0.0 and total specific surface area ratio became 0.0, thereby producing a magnetic recording medium.

The characteristics of the electron conversion characteristics, dynamic friction coefficient, durability, dropout, three-dimensional surface roughness, light transmittance, and the like of the video tapes prepared by the methods of Examples and Comparative Examples were evaluated by the following methods. 1 is shown.

1) RF output

The video tape was mounted on Victor Tech's Video Tech (BR-7000) to record a 100% white signal, and then measured the output during playback, and the RF-output of the video tape obtained here was set to 0 dB, based on this value. The difference was shown.

2) Dropout

After recording the 5-step difference signal on the video tape with the optimal recording current, the attenuation of the video amplifier during playback is 16 dB and the duration is 15 μsec or more, which is regarded as a dropout, and the measurement is continued for 10 minutes, and then the average number per minute It is shown.

3) running durability

Using the durability meter manufactured by Bergman, USA, the magnetic layer of the video tape was contacted with the head, and the time until the magnetic layer was damaged was measured and evaluated in four steps as follows.

A: More than 60 minutes

B: More than 50 minutes-less than 60 minutes

C: More than 40 minutes-less than 50 minutes

D: More than 30 minutes-less than 40 minutes

4) Dynamic Friction Coefficient

The video tape is contacted with a stainless steel drum with a diameter of 4 inches to 180 °, and the tension is applied to the video tape when rotating the drum at a speed of 1.8 m / min by applying a tension of 100 g (T ₁ ) (T ₁ ), The dynamic coefficient of friction was calculated by the following equation.

5) light transmittance

The magnetic recording medium was determined using a light transmittance measuring instrument manufactured by Victor Nippon, Japan, to determine the amount of light transmitted at a wavelength in the range of 800 to 900 nanometers.

Since the VHS standard is 1.2% or less, less than 1.2% is indicated by ○ and 1.2% or more by ×.

TABLE 1

As can be seen from the above table, the magnetic recording medium produced by the method of the present invention has very few defects such as a dropout, compared with the magnetic recording medium of Comparative Example, which is a magnetic recording medium manufactured by a conventional method, and has durability. In addition, it has excellent light transmittance and runability. In particular, it has been found that the electron conversion characteristics, which are important characteristics of the magnetic recording medium, are excellent.

Therefore, according to the present invention, when the magnetic recording medium is manufactured by forming the magnetic layer by applying two layers with different compositions of coating thickness and volume concentration on the nonmagnetic support, not only a high quality magnetic recording medium but also economical cost The savings can be expected.

Claims (1)

Using a coating solution prepared by dispersing ferromagnetic powder and carbon black in a binder solution on a nonmagnetic support, a first nonmagnetic layer adjacent to the nonmagnetic support is formed, and a coating solution in which the ferromagnetic powder is dispersed in the binder solution. In preparing the magnetic recording medium by drying, surface smoothing, hardening and cutting after forming the second magnetic layer, the total volume ratio of carbon black and ferromagnetic powder contained in the first nonmagnetic layer is 1.0 to 7.5, and carbon black And the total specific surface area ratio of the ferromagnetic powder is 2 to 16, the total volume ratio of the carbon black and the ferromagnetic powder in the second magnetic layer is 0.02 to 0.3, and the total specific surface area ratio of the carbon black and the ferromagnetic powder is 0.05 to 0.6. Method of manufacturing a record carrier.